It is known to provide an inflatable occupant restraint system, commonly called an airbag, to dissipate energy of an occupant in a vehicle experiencing sudden deceleration above a predetermined threshold. At the deceleration threshold, the airbag is inflated by an inflation gas directed into the airbag, which absorbs energy resulting from movement of an occupant against the airbag. At times, it may be desirable to control the pressure within the airbag.
One way to control the pressure within the airbag is to vent the inflation gas through a vent opening, so as to dissipate energy absorbed by contact thereagainst. Various devices for venting an airbag are known, including those shown in U.S. Pat. No. 5,839,755 (Turnbull), and U.S. Pat. No. 4,096,065 (Okada et al.). Systems with such devices, while perhaps satisfactorily providing airbag pressure control through venting upon impact of an occupant, necessarily release inflator gas.
With the proliferation of side inflatable restraint systems, or side airbags, it may be desirable to prolong inflation of the side airbag beyond an initial occupant contact therewith, or for an initial period of time beyond initial inflation. The aforementioned venting devices, while suitable for their purpose, may not allow the desired prolonged airbag inflation.
As such, an airbag system may be desirable which provides prolonged inflation of the inflatable restraint, for example, when the inflator gas has cooled, or during conditions requiring inflation beyond an initial event.